Self Powered – The power required for correct operation of a transducer is supplied via the line being measured.

Separately Powered – The power required for correct operation of a transducer is supplied via an external or auxiliary power source, rather than via the line being measured.

Setting Accuracy – The ability to accurately set a knob, switch, or other adjustment to the time delay, or other monitored parameter.

Self Inductance – Self inductance is where the changing magnetic field of a circuit induces an opposing voltage in the same circuit. The rate of change of the current in the circuit and the topography of the circuit (e.g. straight versus coil) will determine the magnitude of the self induced voltage (V induced = self inductance factor * dA/ dt).

Sintered Ferrite – A ceramic composite powder composed of iron (FE) and barium oxide or strontium oxide which has been die pressed and fired (sintered) in a high temperature oven. The “soft” version of the sintered ferrite does not retain its magnetism when the magnetic field is removed. Transformer cores manufactured from this type of material are incorporated into high performance transformer applications.

Snubber Network – A form of suppression network which consists of a series connected resistor and capacitor connected in parallel with the output device. Helps to limit the maximum rate of rise of a voltage. Used to prevent false turn-on of solid state outputs.

Snubber – A resistance/capacitor or diode/resistor circuit used to dissipate transient energy peaks.

Temperature Measurement Device, Bimetallic – A bimetallic measuring device uses the principle that different metals have different rates of thermal expansion. When two metal strips that have been bonded together are heated, one side will expand faster than the other resulting in the pair bending. The angle of the bend can be translated into a temperature reading. Relative to other technologies, these devices are not very accurate. However, they are portable and do not require a power source.

Temperature Measurement Device, Resistive -A resistive temperature device (RTD) uses the principle that electrical resistance of a material changes as the temperature changes. As the temperature rises, the resistance rises in the metal more or less linearly.

Temperature Measurement Device, Thermistor – A thermistor uses the principle that electrical resistance of a material changes as the temperature changes. As the temperature rises, the resistance in a ceramic semiconductor drops nonlinearly with the change in temperature.

Temperature Measurement Device, Thermocouple -A thermocouple uses the principle that when certain materials are bonded together at one end, changes in temperature results in a change in the electromotive force (voltage) between the opposite ends. As the temperature rises, the output emf rises, though not linearly with the change in temperature.

Thermistor – See – Temperature Measurement Device, Thermistor

Thermocouple – See – Temperature Measurement Device, Thermocouple

Thermowell – A thermowell is a pressure tight enclosure designed to accept a temperature sensing element and provide a means to insert that element into a vessel or pipe. A thermowell acts as a barrier between a process medium and the sensing element of a temperature measuring device. It protects against corrosive process media, as well as media contained under pressure or flowing at a high velocity. A thermowell also allows the sensing element to be removed from the application while maintaining a closed system.

Transducer, Current – A device for converting an Alternating Current (AC) electrical signal into a useable DC voltage or current signal for measurement purposes.

Transducer, Pressure – A device for converting a pressure measurement into a useable DC current or voltage signal for measurement purposes.

Transducer, Temperature – A device for converting a temperature measurement into a useable DC current or voltage signal for measurement purposes.

Transducer, Voltage – A device for converting an Alternating Current (AC) electrical signal into a useable DC voltage for measurement purposes.

Total Harmonic Distortion – The ratio between the apparent power associated with higher order harmonics divided by the apparent power associated with the fundamental harmonic.

Transient – Term used to describe power disturbances such as surge, spike, RF (radio frequency) interference, harmonics.

True RMS Amps – The effective value of an ac signal. For an amp signal, true RMS is a precise method of stating the amp value regardless of waveform distortion. An ac measurement which is equal in power transfer to a corresponding dc current.

True RMS Volts – The effective value of an ac signal. For a voltage signal, true RMS is a precise method of stating the voltage value regardless of waveform distortion. An ac measurement which is equal in power transfer to a corresponding dc voltage.

UL 94 – UL Subject 94 is a flammability test. This test is meant to describe and quantify the flammability of plastic materials when exposed to a flame and heat.

UL 94 V-0 – Flammability test rating – highest rating for a vertical burn test (flame extinguished within 10 seconds and no flaming drip).

UL 94 V-1 – Flammability test rating (flame extinguished within 60 seconds and no flaming drip).

UL 94 V-2 – Flammability test rating (flame extinguished within 60 seconds, flaming drips are allowed).

UL 94 H-B – Flammability test rating, horizontal burn – lowest rating (flame slow moving or self extinguishing).

Unbalanced Loads – Refers to an unequal loading of the phases in a three phase system. Imbalances could be the result of unequal resistive or inductive loads on each phase.

Watt – Unit of electrical power. WATTS=E*I*PF

VA – The product of the RMS voltage applied to a circuit and the RMS current (amperes) flowing through it.

VAR(Volt-Amperes Reactive) – The unit of reactive power as opposed to real power (watts)

Wiki – WEB based collaborative software which permits invited users to edit or add material to a common project. An example is the wiki encyclopedia project (en.wikipedia.org/wiki/main_page).

Other uses include; research & development projects, project management, etc.

Zigzag Transformer – A special purpose transformer that has two primary windings for each phase but no secondary windings. Applications include; a) deriving an earth reference point in ungrounded electrical distribution networks, enabling the detection of earth fault currents and b) the detection/ control of harmonic currents in ungrounded electrical distribution networks.